1. Field of the Invention
The present invention relates to systems and processes used in manufacturing integrated device die, such as integrated circuit and laser die, including diode laser die, formed on sapphire substrates. More particularly, the present invention provides for scribing sapphire substrates using solid state UV lasers, and separating the scribed sapphire substrate into die.
2. Description of Related Art
Sapphire Al2O3 is used as a substrate for a variety of devices. The sapphire is a hard material that is optically transmissive, electrically nonconducting and a good conductor of heat. It has become the preferred substrate material in manufacturing of laser diodes. In particular, blue laser diodes and other structures based on gallium nitride GaN and related materials are manufactured on sapphire substrates in large volume.
One bottleneck in manufacturing of die on sapphire substrates is the separation of the die from the substrate. Because sapphire is very hard, the typical process requires the use of a diamond tipped blade to scribe a pattern in the substrate. In one common method, the sapphire substrate having an array of semiconductor structures such as laser diodes formed thereon is placed on an adhesive known as “blue tape,” or “wafer tape.” A diamond blade is used to scribe the substrate. Mechanical stress is used to crack the substrate along scribe lines. The tape carrying the cracked substrate is then stretched to separate the die. A robotic pick and place machine is used to remove the individual die, having typical dimensions in a range of 200 to 500 microns on a side, from the tape.
One major bottleneck in the manufacturing of the die is the cutting process. The diamond blade requires the manufacturer to allocate a relatively wide scribe line, referred to as a “street,” (for example, 40 to 70 microns) on the substrate, reducing the number of die manufacturable on a single substrate. In addition, the diamond tip blade must be operated relatively slowly, requiring as much as 1 and a half hours for a 2 inch diameter substrate. Also, the diamond tips on the blade wear out and must be replaced often, as much as one blade per wafer. Replacement of the blades slows down the process of manufacturing. Also, the blades typically have multiple tips, which must be carefully and precisely aligned for proper cutting each time a new tip is brought on line, and each time a new blade is installed. Finally, the mechanical scribing process causes cracks, which can damage the die and reduce yields. Typical yields for this process have been reported to be about 70%.
It is desirable, therefore, to provide a system and method for scribing sapphire substrates in manufacturing die which is faster, easier to use, minimizes the number of consumable parts, allows for greater density and achieves greater yields than is available using current technologies. Further, it is desirable that such system be compact, safe to operate and low-cost.